Interactive conferencing systems provide users residing in disparate geographic locations the capability to participate in a real time design activity. Typically each user or participant is associated with a computer that is networked with the computers of the other participants. A display device associated with each user is used as a virtual whiteboard to display and receive drawings and other communications pertinent to the collaborative design activity. Each participant has the same copy of the shared drawing in its whiteboard. Each participant engages in the design activity by adding or editing the shared drawing. Alterations to the shared drawing are quickly transmitted to each participant in order to maintain a consistent state of the shared drawing amongst the participants. Thus, the success of such a system relies on an efficient methodology for quickly relaying graphical images to each of the participants.